High-performing catalyst uncovered

16 February 2016

Method devised for making
large quantities of georgeite with unprecedented ability as a catalyst to
produce hydrogen from water

An extremely rare mineral,
found only in two locations around the world, including
an old copper mine in Snowdonia, has been manufactured in large quantities
for the very first time by researchers at Cardiff.

Largely neglected up until now,
the manufactured mineral, known as georgeite, has shown remarkable catalytic
properties and could lead to improved methods for manufacturing some of the
most important products in the chemical industry.

The team, based at the Cardiff
Catalysis Institute, has shown that georgeite is an extremely efficient
catalyst in the process used to produce hydrogen from water, which is an
essential ingredient used to manufacture methanol and ammonia, which form the
basis of hundreds of chemicals including fuels, plastics, paints, solvents and
fertiliser.

Georgeite belongs to a family of minerals known as copper
hydroxycarbonates that are widely used as catalysts in the chemical industry.

Whilst researchers are familiar
with other minerals in this group, such as malachite, aurichalcite and
rosasite, little is known about georgeite due to its exceptional rarity, low
purity, instability and highly disordered nature.

For the first time, the team
have successfully synthesised georgeite in the lab in large quantities and in
its purest form – in nature it is only found as impure deposits.

They did so using a technique
known as supercritical anti-solvent precipitation (SAS), which involves the
creation of a solid material from a liquid solution. The starting material,
otherwise known as the precipitating agent, was supercritical carbon dioxide –
a form of the well-known gas.

The resulting mineral, which
was rapidly made, had a highly amorphous structure which contributes to its
high activity when it came to catalysing reactions.

Professor Graham Hutchings,
Director of the Cardiff Catalysis Institute, said: “We have shown that we can
make large quantities of material that has historically been known as a very
rare material.

“Furthermore, we’ve discovered
the conditions to make a very pure version of this mineral fairly easily,
whereas in nature it is only found as impure deposits.”

Professor Hutchings and his team tested the catalytic
ability of georgeite against commercially used catalysts in the water-gas shift
reaction – an extremely important process in the chemical industry in which
water reacts with carbon dioxide, in the presence of a catalyst, to produce
hydrogen.

“We found that the georgeite
was a superb catalyst in the water-gas shift reaction, and had a much higher
performance compared to the commercial catalyst that is currently used in
industry,” continued Professor Hutchings.

The team also included researchers from the UK Catalysis
Hub, University College London, Diamond Light Source, University of Liverpool,
Technical University of Denmark, Lehigh University and Johnson Matthey.